Flagella of Euglena are being analyzed biochemically and structurally as a potentially useful source of non-brain derived microtubule protein. These flagella have an unusual, large paracrystalline rod which from preliminary data appears to be composed of microtubular protein. These paracrystals together with axonemal microtubules can be selectively solubilized with relatively mild treatment. Efforts are being made to recover the proteins in a form still capable of repolymerization or copolymerization with brain tubulin. The aim here is to develop an in vitro microtubule assembly system not of brain origin since it is not known whether the properties of brain tubulin are unique to brain or of general significance. Furthermore, brain tubulin in vitro does not respond to many drugs which have dramatic effects in other system in vivo. A second phase of this project is designed to further define the proteins which give the surface pellicle its form and controlled plasticity. Previous efforts have yielded a submembrane protein which has been partially characterized and identified as the component responsible for pellicle form and probably pellicle movement. Attempts will be made to further identify the protein and its possible relationship to actin, spectrin and other submembrane proteins found in more highly developed organisms. BIBLIOGRAPHIC REFERENCES: Hofmann, C., and Bouck, G.B. l976. Immunological and structural evidence for patterned intussusseceptive growth in a unicellular organism. A postulated role for submembrane proteins and microtubules. J. Cell Biol. 69: 693-716. Bouck, G.B. and Brown, D. L. l976. Self-assembly in development. Ann. Rev. Plt. Physiol, in press.